| Case period | Control periods |
---|
Definition I | Last day | Last day |
Definition II | Last day | Half or more days |
Definition III | Last day | Any 1 day |
Definition IV | Any 1 day | Any 1 day |
- Last day = exposure status of the period was the exposure status on the last day; Half or more days = exposure status of the period is defined as ‘exposed’ if at least half of days during the period was exposed and ‘unexposed’ otherwise; Any 1 day = exposure status of the period is defined as ‘exposed’ if at least 1 day during the period is exposed and ‘unexposed’ otherwise